ORIGIN OF BASAtr. 285 



none J yet, by an attentive examination of clifFerent writers on pacts and ob- 

 volcanic subjects, I find pretty good light is thrown upon this ^^^^^JJ^^'^^i^Jlt 

 topic. The evidence I will adduce, is, I confess, indirect, and in ,he county 

 the mention ofthe subject incidental; yet 1 do not, therefore, of Antvim ; ad- 

 . , J . T , • ' ■ 4 ] duced to show 



give it less weight; for, siiace 1 engaged m potemic natural o^^^ ;^ j^^ ^oj 



history, I have discovered, that a reliance on positive asser- volcanic, ^ 

 tion is not the surest mode of obtaining truth. 



The first evidence I shall produce, to the effect of actual 

 glowing lava upon calcareous substances, is that of Lord Win* 

 Chelsea, whose letter to King Charles 11. (quoted by Sir 

 William Hamilton), giving an account of the great eruption of 

 ./Etna, in 1G69, says: " Where the streams of lava meet with 

 rocks and stones ofthe same matter (as many are), they melt 

 and go away with the fire. Where they meet with other com- 

 positions (calcareous, no doubt), they turn them to lime or 

 ashes." 



Mr. Ferber's testimony on the subject is decisive. He gives 

 us, in his eleventh. letter, a catalogue of ejections from Vesu- 

 vius; of which No. 6 is, by his account," white lime-stone or 

 marble, in loose pieces, some burnt and calcined.'' He ob- 

 serves, " they are found, likewise, in the ashes and lava, and 

 then constantly calcined and farinaceous." Again, letter 14, 

 he says, " at Monte Albano, the lava, as well as the piperino, 

 contain calcined fragments of lime-stone." 



Tozzetti di Targioni, in his elaborate account of the mine- 

 ralogical productions of his own country, confirms Ferber's 

 testimony, as to the uniform calcination of calcareous sub- 

 stances.* 



Since, then, glowing lava uniformly calcine; the calcareous 

 substances it comes in contac^t with, and basalt produces no 

 effect whatsoever upon them, are we not to conclude, that it 



- did 



* Tozzetti is full on the subject: He says (page 448, Vo-1. IX ) 

 ♦' Se materiali sieno di nalura vitresccnii, formeranno lave vctrine, sc 

 calcarei o upiri, le .foririeranno poherose." 



Page 250. " In essi (lave vesuviane) si vedono rrvisti materie ve- 

 trificate, con matgrie calcinate, e con allri quasi non punto tocciie drj 

 fuoco." 



Page 252. *' II fuoco volcanico, nellq vcscere delta montagna di 

 SanFiora, abbia ofFeso — fuse le massolette di metalli, e calcinate o- ve- / 

 trificate, secofido la loro attitudine altre sostauze." 



